The “Doppler effect” refers to the universally perceived change in the

Question

The “Doppler effect” refers to the universally perceived change in the apparent pitch of a sound when that sound is approaching or receding from the listener. Specifically, whenever the distance between the listener and the source of the sound is decreasing, the sound will be perceived by the listener as higher than its true pitch; whenever that distance is increasing, the sound will be perceived by the listener as lower than its true pitch. If the distance between the listener and the source is not changing, the listener will perceive the true pitch of the sound.

If the above principle holds, which of the following should be observed as an eastward-traveling train is approached by a westward-traveling train that is blowing its horn?

If the above principle holds, which of the following should be observed as an eastward-traveling train is approached by a westward-traveling train that is blowing its horn?

(A) Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound lower than the true pitch.

(B) Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound lower than the true pitch.

(C) Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound higher than the true pitch.

(D) Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch.

(E) Passengers in both trains should hear a sound that is higher than the true pitch.

aditya8062 · Answer

D it is :  Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch . --------------> people in W train will hear same pitch as they are in the train and people in E train will hear increased pitch as two train are approaching each other !!

Skywalker18 · Answer

The “Doppler effect” refers to the universally perceived change in the apparent pitch of a sound when that sound is approaching or receding from the listener. Specifically, whenever the distance between the listener and the source of the sound is decreasing, the sound will be perceived by the listener as higher than its true pitch; whenever that distance is increasing, the sound will be perceived by the listener as lower than its true pitch. If the distance between the listener and the source is not changing, the listener will perceive the true pitch of the sound. 
Type - Inference
If the above principle holds, which of the following should be observed as an eastward-traveling train is approached by a westward-traveling train that is blowing its horn?

A.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound lower than the true pitch. -The source of sound is not in eastbound train and hence passengers on it will hear a different pitch
B.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound lower than the true pitch. - Since the distance between trains is decreasing, the passengers will hear a pitch higher than the true pitch
C.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound higher than the true pitch. - -The source of sound is not in eastbound train and hence passengers on it will hear a different pitch
D.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch. -Correct
E.Passengers in both trains should hear a sound that is higher than the true pitch.- The passengers on westbound train will hear the true pitch

Answer D

guptarahul · Answer

It is clear that

1 whenever the distance between the listener and the source of the sound is decreasing, the sound will be perceived by the listener as higher than its 
 true pitch
 
 2 whenever that distance is increasing, the sound will be perceived by the listener as lower than its true pitch. 
 
 3 If the distance between the listener and the source is not changing, the listener will perceive the true pitch of the sound

A.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound lower than the true pitch. Incorrect
B.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound lower than the true pitch. Incorrect
C.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound higher than the true pitch. Incorrect
D.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch.  Correct using point 1 and 3 
E.Passengers in both trains should hear a sound that is higher than the true pitch. Incorrect.

KUDOS :P

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LakerFan24 · Answer

The “Doppler effect” refers to the universally perceived change in the apparent pitch of a sound when that sound is approaching or receding from the listener. Specifically, whenever the distance between the listener and the source of the sound is decreasing, the sound will be perceived by the listener as higher than its true pitch; whenever that distance is increasing, the sound will be perceived by the listener as lower than its true pitch. If the distance between the listener and the source is not changing, the listener will perceive the true pitch of the sound.

If the above principle holds, which of the following should be observed as an eastward-traveling train is approached by a westward-traveling train that is blowing its horn?
> Classify Q: INFERENCE

A.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound lower than the true pitch.
- eastbound train should not hear the "true pitch" b/c westbound train is reducing distance & blowing its horn. eastbound train should hear pitch HIGHER than true pitch

B.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound lower than the true pitch.
- same as "A" (eastbound train should hear pitch HIGHER than true pitch)

C.Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound higher than the true pitch.
- same as "A" (eastbound train should hear pitch HIGHER than true pitch)

D.Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch.
- correct as is.

E.Passengers in both trains should hear a sound that is higher than the true pitch.
- passengers in westbound train should not hear a sound higher than true pitch b/c they're in the train that is originating the sound. if anything, they should hear the true pitch

* see how far you can get just from understanding 1/2 of the info given? (key: understand what is happening with eastbound train and you can eliminate 3 A/C!)

Kudos please if you find helpful

VijayShanker · Answer

D wins.

Since the westbound train is blowing its horn, the westbound train is “the source of the sound.” Therefore, the passengers on the westbound train are traveling along with the source of the sound, and thus are neither approaching the source nor receding from it. Hence the westbound passengers should hear the true pitch of the sound.

According to the passage, the passengers in the eastbound train are approaching the source of the sound, the westbound train; the distance between the eastbound passengers and the sound is decreasing. Therefore, according to the given description of the Doppler effect, the eastbound passengers should perceive a sound that is higher than the true pitch.

anothermillenial · Answer

The passage states that the “Doppler effect” affects the listener’s perception of the sound. If the distance is decreasing, the listener hears it as HIGHER. If distance increasing, the listener hears it at LOWER.

If a eastward-travelling train is approached by a westward-train, the distance between them must be decreasing. Therefore, the eastward-train must be perceiving the source of the sound (from the westward train) as HIGHER than true pitch, while the westward train hears it like it is.

(A) Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound lower than the true pitch.  
No, the source of the sound is the westward train.

(B) Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound lower than the true pitch.  
Half right. The passengers of the eastbound train would only hear the sound as LOWER if the trains are moving in opposite directions.

(C) Passengers in the eastbound train should hear the true pitch of the horn; passengers in the westbound train will hear a sound higher than the true pitch.  
Again, the eastbound train is NOT the source of the sound.

(D) Passengers in the westbound train should hear the true pitch of the horn; passengers in the eastbound train will hear a sound higher than the true pitch.  
This is correct!

(E) Passengers in both trains should hear a sound that is higher than the true pitch. 
Almost picked this but then realised that the principle only affects the LISTENER.

dcummins · Answer

Distance decreasing from source = Higher Pitch
Distance increasing from source = Lower Pitch
Distance same from source = true pitch

The trains in question are essentially converging, so the passengers onboard the train generating the sound will hear the same tone, but the passengers onboard the train approaching the train generating the sound will hear an increasing pitch.

D matches up to the principles.

Bunuel · Answer

OFFICIAL EXPLANATION

Since the westbound train is blowing its horn, the westbound train is “the source of the sound.” Therefore, the passengers on the westbound train are traveling along with the source of the sound, and thus are neither approaching the source nor receding from it. Hence the westbound passengers should hear the true pitch of the sound.

According to the passage, the passengers in the eastbound train are approaching the source of the sound, the westbound train; the distance between the eastbound passengers and the sound is decreasing. Therefore, according to the given description of the Doppler effect, the eastbound passengers should perceive a sound that is higher than the true pitch.

(A) Passengers in the eastbound train do not hear the true pitch of the horn; passengers in the westbound train do.

(B) It is true that the westbound passengers hear the true pitch; the eastbound passengers, however, hear a sound that is higher than the true pitch.

(C) Passengers in the eastbound train do not hear the true pitch of the horn; passengers in the westbound train do.

(D) CORRECT.  Westbound passengers do hear the true pitch of the sound. Eastbound passengers do hear a sound that is higher in pitch than the true sound.

(E) It is true that eastbound passengers hear a sound that is higher than the true pitch; the westbound passengers, however, hear the true pitch.

siddhantvarma · Answer

I have a doubt here if someone can clarify? What does "approached by a westward travelling train" mean? It appears that the trains are converging, but then what does "westward travelling" imply here? Is it to confuse the readers? I understood "westward traveling" as diverging train, a train traveling in the west against a train traveling east so passengers in the eastward train should hear lower than true pitch since the distance between the two is increasing?

The “Doppler effect” refers to the universally perceived change in the

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The “Doppler effect” refers to the universally perceived change in the

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